1. Field of the Invention
The invention concerns a wheel for in-line roller skates namely the type having aligned or in-line wheels, which has a special configuration of its tire rim or hub so as to permit a reinforced grip of the toroidal cover of the wheel tread or tire which is directly in contact with the ground.
2. General State of the Art
It is known that in roller skates having aligned wheels, the wheels undergo violent stresses, especially when such roller skates am used on roads rather than on skating rings having smooth surfaces especially built for this purpose.
The stresses to the wheels are caused both by the irregular surface of the road and by the stresses which are encountered during the rotation of the wheels on the sliding surface. In addition, such wheels hardly rotate with their axis parallel to the roadway but they very often have a slanted axis in relation to the roadway and, therefore, the impact reaction which is discharged on the tire, tends to tear the tire from the hub.
It is also known that the tire or tread cover, which has a toroidal shape, is made of plastic material, usually thermosetting polyurethane, the chemical characteristics of which do not have an affinity with the plastic material forming the tire rim or hub to which the tire clings. The hub is usually made of polyamide or of another material which does not mix or melt with the polyurethane material.
Thus, as a result of the stresses the wheels undergo when the roller skates are used, it is impossible to closely combine together the materials forming the tire and the hub. It therefore is of primary importance to obtain some anchorage points between the tire and the hub which is sufficient to prevent such separation.
A hub or tire rim for wheels of roller skates shown in U.S. Pat. No. 5,028,058, has two rings concentric with the wheel pivot opening or hole. The rings have an increasing diameter and are connected with the hole through essentially radial sectors. The outer ring is covered by the casting of polyurethane material of the tire and extends to the transversal openings between the outer and inner concentric ring, so as to form transversal segments of cast material. The segments hold the tire to the more external ring of the hub.
Experience has shown that this type of anchorage does not prevent the wheel from becoming damaged by the shocks and by the strong transversal stresses. As a result, the transversal segments become cut and the tread eventually rotates freely on the hub with evident damage to the skate and danger to the user of the roller skate.